Personal health and fitness has become increasingly popular over the recent years. As a result, health club memberships and personal fitness equipment sales have increased. Personal fitness equipment is especially popular because it allows individuals to exercise on their own time while in the convenience and privacy of their own homes. Exercise equipment generally uses weights as the primary source of resistance. However, other sources of resistance such as flexible bands or hydraulics can also be used. Flexible bands are often found on exercise equipment so that a user is not required to maintain and store bulky weights.
Items such as springs are generally not used as a source of resistance for exercise equipment. This is because many spring motors have a very short life expectancy and are not suitable for repetitive use. Additionally, spring motors generally do not exert any resistance at their resting position. Therefore most spring motors would not provide an experience similar to that of using free-weights or stacked weights.